A hydraulic excavator as a construction machine performs a “swing boom raising” operation that is a combined operation of raising a boom while swinging the boom in order to discharge excavated earth, sand, and the like onto a cargo of a dump truck. It is a well-known technique to reduce a swing speed at this time from that at a time of a sole swing operation or to increase a boom raising speed from that at the time of the sole swing operation, with a view to avoiding the contact of a bucket with the dump truck or with an excavation slope.
In recent years, the development of a hybrid excavator including an electric swing motor that is an alternative to a conventional hydraulic swing motor or that assists the hydraulic swing motor in functioning is underway for reducing fuel cost. Even the hybrid excavator of this type needs to maintain operability for the swing boom raising operation similarly to the conventional hydraulic excavator.
There is disclosed a method for maintaining the operability for the swing boom raising operation by determining, by the hybrid excavator including the electric swing motor as an alternative to the hydraulic swing motor and including “operation detection units” detecting a boom operation and a swing operation, that the swing boom raising operation has been executed on the basis of a signal detected by this operation detection unit, and then suppressing output power of the electric swing motor, compared with output power at a time of the sole swing operation (refer to, for example, Patent Document 1).